Memtest86+ test failed Z77A-G45 + Corsair Vengeance 16gb

Question

Just got board back from RMA and ram memtest86+ on new ram.  No system instability or BSOD just been having really bad luck lately.  New GPU bought lasts Thursday seem dodgy (rattling fan, and cannot handle a small overclock, which other people had no problem with)  and though I might take a look at the new ram also.
Memtest86+ v4.20 - 
2 sticks - Dimm 2 & 4 error on in first pass.  Correct CAS in Bios and Memtest 10-10-10-27
1 stick - Dimm 2 error first pass. Bios CAS 10-10-10-27.  Memtest 6-6-6-20 -both sticks-
1 stick - Dimm 3 error first pass. Bios and Memtest 10-10-10-27 -both sticks-
did not try Dimm 1 cause heatsink was in the way and Dimm 4 since it failed in the first two Dimms already.
Little searching on google and 6-6-6-20 timing seem very common in Memtest86+.  2 out of the 4 Dimm alway show 6-6-6-20 timing while the other corresponds correctly
I didn't try to manually set Timing since in dual channel mode timing is correct and and though that is how its suppose to work or 6-6-6-20 was a Memtest bug.
Now Memtest86+ 5.00b1 - with ivy bridge support
2 sticks - Dimm 2 & 4 error on in first pass.  Correct CAS in Bios and Memtest 10-10-10-27 (later found they where false positives)
1 stick - Dimm 2 error first pass. Bios CAS 10-10-10-27.  Memtest 6-6-6-20
1 stick - Dimm 3  Bios and Memtest 10-10-10-27 no errors after 8 passes
Testing stick 2 now.  Is it safe to say that if this stick does 8 passes with no errors then the ram is good and though Dimm 2 has wrong timing in Memtest single channel.  In dual channel Dimm2 & 4 the timing is correcty that is fine also.  Or should I manually set the timing and test every Dimm slot.
Thanks

Answer 1

Memtested the good stick of ram agian in DIMM2 before bringing it back to exchange.
First time with just XMP profiles and it failed before the first pass.
Then set timing manually and had no erorrs for 1 pass,   though memtest still showed the CAS as 6-6-6-20 while the Bios and CPUz had the correct 10-10-10-27. Then tried DIMM 4 just to see what the timing was and it was the right one just like DIMM 3. 
Also used the Windows 8 built in memory diagnostic. one stick at a time and it caught the problem with the bad stick.  And just used it again with both new sticks installed and it passed.
Just wondering if there are other memory diagnostic tools I can try using.  Memtest 5.0 has a lot of glitches, freezes, false postives, and 4.20 from what I gather does not support Ivy Bridge